Regardless from what I've seen.. I can hardly think of a reason why aliens would hate chairs so much. Could you describe to me a "in character" reason why a alien would atomize a chair without using its acid?

Why do aliens hate chairs so much anyways. WHAT DID THE CHAIRS EVER DO TO YOU?

This is intentional. Aliens usually destroy everything in their path so they can put up their hives. Yes, this includes chairs. You won't see any non-alien creations in a hive unless it's the structure of whatever they are hiding out in.

Anything that doesn't come from them or their sisters in the first place is impure.

Not sure if anyone has actually played xeno in here other than the OP, but anything that can be destroyed as a xeno without acid will leave something behind, whether it be metal or the base parts of the object (Rack parts, table parts, etc.) for some reason the only exception for this is chairs, which is most likely a bug.